The argument goes like this:
Person A is in such a bad situation that A will accept a job that is terrible!
Prohibiting the job has a good chance of making A worse off (usually, A will accept the job if A thinks it is an improvement over the current situation)
However, we can let A accept the job, and then try to offer A even better alternatives!
It is also a more physically oriented job that carries some risk of disease exposure, really shouldn't be worked sick, and some accounts mention an emotional toll and an emphasis on appearance. Individually all aspects aren't unique and some have more severe magnitudes.
Given the income is higher than many other available jobs it could be easy to become dependent upon it for income. A good ethical reason for support is that consent is an ongoing process.
Interesting. Do they have social services for those that wish to quit computer programming? Or quit hair dressing?
The fact that there needs to be a social service around this particular profession is indicative that this particular profession is probably harmful to the service provider and it probably also means that this isn’t a profession that a girl willingly accepts and perhaps there is value to not promoting this industry.